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md: set MD_CHANGE_PENDING in a atomic region

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Some code waits for a metadata update by:

1. flagging that it is needed (MD_CHANGE_DEVS or MD_CHANGE_CLEAN)
2. setting MD_CHANGE_PENDING and waking the management thread
3. waiting for MD_CHANGE_PENDING to be cleared

If the first two are done without locking, the code in md_update_sb()
which checks if it needs to repeat might test if an update is needed
before step 1, then clear MD_CHANGE_PENDING after step 2, resulting
in the wait returning early.

So make sure all places that set MD_CHANGE_PENDING are atomicial, and
bit_clear_unless (suggested by Neil) is introduced for the purpose.

Cc: Martin Kepplinger <martink@posteo.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: <linux-kernel@vger.kernel.org>
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
This commit is contained in:
Guoqing Jiang
2016-05-03 22:22:13 -04:00
committed by Shaohua Li
parent fe67d19a2d
commit 85ad1d13ee
6 changed files with 40 additions and 23 deletions
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4
drivers/md/raid5.c
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@@ -2514,8 +2514,8 @@ static void raid5_error(struct mddev *mddev, struct md_rdev *rdev)
set_bit(Blocked, &rdev->flags);
set_bit(Faulty, &rdev->flags);
set_bit(MD_CHANGE_DEVS, &mddev->flags);
set_bit(MD_CHANGE_PENDING, &mddev->flags);
set_mask_bits(&mddev->flags, 0,
BIT(MD_CHANGE_DEVS) | BIT(MD_CHANGE_PENDING));
printk(KERN_ALERT
"md/raid:%s: Disk failure on %s, disabling device.\n"
"md/raid:%s: Operation continuing on %d devices.\n",